Hi nohorn.
Let's "cut to the chase" here, assuming that you have a Stage 1 breast cancer and whether it is treated by surgery/DXT or therapeutic measures, the 5 year survival rate is almost 100%, so lifespan is not an issue.
Mastectomy/DXT or lumpectomy/DXT is a well established and popular choice, but as 237SJ mentioned, the side effects of drugs may not be a problem, although, they are significant.
You are 75 years of age and I presume you have no history of heart attacks, strokes or high blood pressure, as the latter may mitigate against choosing Hormone Therapy, and surgery, although has issues, would not be a problem for you.
If you were a relative of mine seeking my advice, i would suggest mastectomy/lumpectomy followed by DXT.
Remember, my advice may be biased.......ask a surgeon a medical question and you will get a surgical answer ;-)..........discuss it with the Oncologist and Radiotherapist............but you will have the final say.